The present invention relates to a device for the holding down and guiding of plates of sawed lumber on a wood working machine to be machined on either or both of their flat faces and advanced along a straightedge provided on the wood working machine.
Wood working machines for providing one or both faces of plate-shaped lumber with grooves and/or bores, or for separating such plates into smaller pieces, conventionally include a workpiece feed mechanism for advancing the workpiece either in one direction only or in opposite directions. Such feed mechanism advances the workpiece plate stepwise along the straightedge on the machine that extends in the direction of feed movement, whereby one of the trimmed longitudinal edges of the workpiece plate is in close contact with the straightedge.
The exact course of saw cuts and/or the laying of a pattern of bores and grooves in a workpiece plate hinges on the ( accuracy of the alignment of the workpiece plate relative to the straightedge over the entire feed distance. However, the proper alignment and/or abutment of the particular trimmed longitudinal edge of a workpiece plate with the straightedge poses certain problems because the workpiece feed mechanism grips workpiece plates having a length of 3 meters to a maximum of 5 meters at their rear ends by means of clamps to move the workpieces along. So, at a workpiece length of several meters, the guiding of the end portion of the workpiece plate that is opposite the feeding part proper of the feed mechanism is rather unstable relative to its plane of support which is perpendicular to the straightedge. Accordingly, with conventional devices an accurate positioning of the trimmed edge of the workpiece plate against the straightedge on the machine during the feed movement cannot always be ensured even if the part of the feeding mechanism that actually effects the advancing of the workpiece is properly installed and guided.
The object of the invention therefore resides in improvements on the conventional workpiece feed mechanism of wood working machines so as t ensure a steady reliable contact between the trimmed longitudinal edge of the workpiece and the straightedge of the machine over the entire feed distance.
This is accomplished by the characterizing features of the claimed invention, as described more fully hereinbelow.